Functional Description
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor 30-45

30.4.2.2 Transmit Frame Control Word (TFCW)

Figure 30-40 shows the format of the transmit frame control word.

20 NO Receive Nonoctet Aligned Frame. Written by the FEC. A frame that contained a number of
bits not divisible by 8 was received, and the CRC check that occurred at the preceding byte
boundary generated an error. This bit is valid only if the L-bit is set. If this bit is set the CR
bit will not be set.
19 Reserved, should be cleared.
18 CR Receive CRC Error, written by the FEC. This frame contains a CRC error and is an integral
number of octets in length. This bit is valid only if the L-bit is set.
17 OF Overrun, written by the FEC. A receive FIFO overrun occurred during frame reception. If
this bit is set, the other status bits, M, LG, NO, SH, CR, and CL lose their normal meaning
and will be zero. This bit is valid only if the L bit is set.
16 TR Truncated Receive Frame. Will be set if the receive frame is truncated (frame length > 2047
bytes). If the TR bit is set the frame should be discarded and the other error bits should be
ignored as they may be incorrect.
15–11 Reserved, should be cleared.
10–0 FRAME_
LENGTH
Frame length depends on the L (buffer position) bit:
If L = 0, then the frame length value is only the number of octets received.
If L = 1, then the frame length value includes CRC.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Field TC ABC
1514131211109876543210
Field —

Figure 30-40. Transmit Frame Control Word Format (TFCW)

Table 30-46. TFCW Field Descriptions

Bits Name Description
31–27 Reserved, should be cleared.
26 TC Transmit CRC, written by user
0 End transmission immediately after the last data byte.
1 Transmit the CRC sequence after the last data byte.
25 ABC Append Bad CRC, written by user
0 No effect
1 Transmit the CRC sequence inverted after the last data bye (regardless of TC value)
24–0 Reserved, should be cleared.

Table 30-45. RFSW Field Descriptions (Continued)

Bits Name Description